Current supply circuit for electronic safety ski bindings

ABSTRACT

A power supply for the release circuitry of an electronic ski binding having a plurality of electrical sources, switches for controlling the connecting of the respective electrical sources to the release circuitry, and comparator circuits for actuating the appropriate switches to connect the electrical source having the highest electrical potential to the release circuitry.

The invention relates to a current supply circuit for electronic safetyski bindings comprising a battery feeding a releasing circuit andfeeding the electronic circuit which receives by way of converterssignals corresponding to the respective forces acting on the leg of theskier and which delivers a releasing signal to the releasing circuit onthe occurrence of forces endangering the skier's leg.

The safety of electronic safety ski bindings depends decisively on thecurrent supply. If only one battery is provided to energize electronicsafety ski bindings, the binding is useless if this battery fails, sothat a considerable safety risk can occur if the current suddenly fails.

It is therefore the problem of the invention to provide a current supplycircuit for electronic safety ski bindings that ensures adequate safetyeven when a battery feeding the binding fails or its capacity dropsbelow a level maintaining the safety functions.

According to the invention, this problem is solved in that at least twobatteries are provided which are so connected to the electronic circuitand releasing circuit by way of an electronic control circuit that onlyone feeds same, and that the control circuit switches the current supplyto the other battery when the capacity of the first battery has droppedbelow a limiting value which, with an adequate safety factor, is abovethe level maintaining the functioning of the electronic circuit andreleasing circuit. The current supply device of the invention ensuresthat, after one battery fails, the other is available as a reservebattery which maintains all safety functions of the electronic binding.The current supply circuit according to the invention thereby not onlyprovides increased safety against current failure but also maintains theoperability of the binding over a longer period because each of the twobatteries undertakes the energization of the electronic binding as longas its capacity is adequate.

In a further embodiment of the invention, the respective batteryseparate from the electronic circuit and releasing circuit feedsadditional safety circuits having a lower current consumption. Theseadditional safety circuits can be circuits automatically setting thethreshold value or circuits making additional measured values available.They may also be circuits increasing the comfort as well as themanipulation of the binding. The particular construction of these safetycircuits is not the subject of the present invention.

If these safety circuits are fed by a lithium battery which is heldready, a low dissipation of current from this battery is desired becauseits operative condition is ensured only when taking a low current fromit over a prolonged period. With other types of batteries thedissipation of current for the additional safety circuits would likewisenot lead to marked weakening of the battery.

When the capacity of the battery has dropped to below the limitingvalue, its capacity is still sufficient for feeding the safety circuitsand thus relieve the battery which maintains the safety functions.

In a further embodiment of the invention, acoustic and/or opticalwarning means are provided to indicate a drop in the capacity of abattery below the limiting value. The skier will then know that heshould replace this battery for a new one at the next opportunity.However, the discharge or failure of a battery alone will not yet renderthe binding useless.

According to an inventive development, an electronic control circuit isprovided which connects the condenser storing the charge for thereleasing pulse to the electronic circuit as a source of current supplywhen the current supply to the electronic circuit by the battery isinterrupted. Such interruptions can occur for short periods for examplein the case of vibrations. The low discharge of the releasing condenserduring such short time intervals is acceptable because it is stillcharged sufficiently to deliver an adequate surge of current to theelectromagnet controlling the releasing mechanism if a releasing pulseoccurs.

In a further embodiment of the invention, additional safety is obtainedin that an electric control circuit is provided which, when the capacityof the second battery drops below the limiting value, interrupts all thecircuits not directly serving the safety release.

A feature will now be described with which the operating reliability ofan electronic safety ski binding is increased in that other sources ofcurrent are employed when the main or reserve current supply failsbecause the battery is exhausted or there are faults in the circuit.Three redundant current sources are provided, namely two independentsets of batteries and condensers of large storage capacity whichnormally supply the energy necessary for actuating the electromagneticreleasing means.

The operation of the system is based on the function of logic circuitswhich ensure that the main current source is switched off and thereserve source switched on if the voltage of the main source drops belowa predetermined value. On switching over, an acoustic or optical warningsignal is produced so that the skier knows that the current source inthe ski binding must be recharged or replaced. As long as this has notbeen done, the warning signal will be repeated every time the ON-OFFswitches are actuated when stepping into the binding. The reserve sourceof current has the same lifespan as the main source. If the skierignores the indication of the exhausted main source several times andcontinues to use the binding until the voltage of the reserve sourcealso drops below the threshold value, a second (different) acoustic oroptical warning signal will be produced and the safety circuit ensuresthat only the most important consumers remain switched on, e.g. forcereceivers, the voltage frequency converters and the releasing means. Ifthe safety circuit disconnects a battery from the current supply rail ofthe system, this battery normally still has a life of 20 to 30 hours.Now, in order that the system does not become inoperable when the maincurrent source and the reserve source have been discharged down to thethreshold voltage, the safety circuit selects the strongest of the threecurrent sources consisting of the main battery, the reserve battery andthe aforementioned storage condensers. This ensures that the threecurrent sources are used uniformly until the voltage to which thecondensers are charged no longer suffices to actuate the electromagneticreleasing device, so that the binding can no longer operate. Thequestion as to how the system is to behave just before reaching thiscondition is still open. Should a last warning signal be given? Shouldthe binding open even though it might just be in use? Or may the skiercontinue until he presses the releasing button and he can free himselfof the binding only by taking off the ski boot or operating a mechanicalauxiliary releasing device? Experience will show which solution is to bepreferred.

The consecutive use of the current sources in the manner described aboveincreases the reliability of the ski binding because the safety circuitwill be continuously supplied with current even if the mechanicalswitches open momentarily as a result of strong impacts or oscillations.Since the electronic switches for starting the storage condensers arenot influenced by such an impact, an uninterrupted current supply isensured during the entire normal operation of the ski binding.

The operation of the system will be described with reference to thedrawings, in which:

FIG. 1 is a block diagram with the most important functional components,and

FIG. 2 is a circuit of one embodiment.

According to FIG. 1, mechanical switches 1 and 2 are, as hereinbeforedescribed, operated when the ski boot is inserted in the binding. Onlythe higher voltage is applied to the safety circuit. This is normallythe voltage of the reserve current source because the main sourceinitially feeds the entire processing system and therefore has a lowervoltage. The low current consumption of the reserve current source isintentional and advantageous because it is intended to use lithiumbatteries in the ski binding, which are prevented, by a constantwithdrawal of a weak current, from becoming dormant, which often leadsto difficulties with lithium batteries. The comparator circuits detectwhen the voltage of one of the current sources drops below thepredetermined value at which change-over is to take place and emit thesignals for causing another current source to be connected to thecurrent supply rail of the system. The comparator circuits also producetwo warning signals, namely one for the main current source and one forthe reserve source. After switching off the reserve current source, thesystem is switched to economy operation, i.e. only the most importantconsumers remain connected.

FIG. 2 is a detailed circuit diagram of an embodiment with doublyredundant current supply. The description will first be of normaloperation where both batteries are sufficiently charged and no faultshave occurred in the circuit. Operation commences when the mechanicalswitches SW 1 and SW 2 are closed by stepping into the ski binding. Thisapplies the main current source V_(B1) to the diode D1 and the reservecurrent source V_(B2) to the diode D2. The higher voltage is transmittedby the respective diode so that a blocking voltage is applied to theother diode and the voltage V_(T) is obtained which is required tooperate the electronic devices of the safety circuit. The resettingsignal PWRUP (system switched on) applied to FF₁, FF₂ and FF₃ ensuresthat the large signal is applied to all outputs Q on commencement ofoperation, so that the signal Q₁ transmitted through the OR gate G1causes the electronic switch SW3 to close and the system voltage to beapplied to +V. Since the small signal is at the output Q1 of FF₁, thesmall signal is also present at the output of the AND gate G4 and theswitch SW4 is open. The reserve source of current V_(B2) is thereforeseparated from the current supply rail +V. The amplifier A1, resistor R1and Zener diode Z1 form a circuit for delivering a stabilised voltageV_(R) amounting to 1.2 V in this example. The resistor R1 is so smallthat the current flowing through the Zener diode Z1 suffices to maintainthe reference voltage of 1.2 V until the voltage of the current sourceconnected to the current supply rail +V drops to below the predeterminedthreshold value.

The amplifier A1 is a voltage follower which defines a voltage source oflow impedance transmitting a stabilised voltage to the parts of thesystem requiring same. The amplifier A2 is a comparator of which theminus input is connected to the tapping of the voltage dividerconsisting of the resistors R2 and R3. The voltage divider voltageV_(F1) drops to 1.2 V when the output voltage of the main current sourceV_(B1) has dropped to such an extent that the reserve current source isconnected to the system. In this case, the large signal appears at theoutput of A2, so that a warning signal FAIL-1 is produced. At the sametime, the voltage rise effects keying of FF₁ so that the large signalappears at the output Q1 and the small signal at the output Q₁. FF2 hasthe same function with respect to the battery V_(B2). In the normalcourse of events, the small signal is now at output Q₂ and the largesignal at output Q₂ because the battery V_(B2) should now besubstantially fully charged. For the same reason, the comparator A4having V_(B1) and V_(B2) connected to its inputs transmits the largesignal to the NOT element I₁. With a small signal at Q₁ and at theoutput of I₁, small signals will be both inputs of the OR gate G1, sothat a small signal will also be present at its output. Consequently,there will also be a small signal at the output of gate G3 even thoughthe OR gate G5 now applies a large signal to the other input of G3, ofwhich the one input has a large signal applied to it by the output Q₂.

When the small signal appears at the output of G3, the switch SW3 opensso that the battery V_(B1) is disconnected from the current supply rail+V. Since the large signal is at output Q1, it is also at the output ofA4 and the output of G5. On the appearance of the large signal at theoutput of the AND gate G4, the switch SW4 now closes so that the batteryV_(B2) is applied to the current supply rail. The preceding descriptionrelates to when V_(B1) is switched off after its normal exhaustion andV_(B1) is switched on. Without a third source of current, the AND gateG3 would be unnecessary and the amplifier A4 would repeatedly change itscondition and apply to the current supply rail +V always that batteryV_(B1) or V_(B2) which has the higher voltage. There will now follow adescription of how the third current source is connected to the system.

When V_(B2) is so exhausted that the large signal appears at the outputof the comparator A3, the warning signal FAIL-2 is produced and thevoltage rise causes the keying over of FF2. As a result, the largesignal appears at the output Q2 and the small signal at output Q₂. Byreason of the large signals at the outputs Q1 and Q2, the large signalappears at the output of the AND gate G6 and FF3 is therefore keyedover. The system is thereby switched to NINPWR (economy operation) andthe small signal appears at the output Q₃ so that the switches for allthose functions of the system which are not absolutely essential forreleasing the binding open. The small signal is now at the outputs Q₁and Q₂ so that the small signal is present at two of the four inputs ofthe OR gate G5. As previously mentioned, the third current source isformed by the storage condensers serving to feed the electromagnets ofthe electromagnetic releasing means. These condensers are designatedC_(SOL). The resistors R4 and R5 define a very high ohmic voltagedivider to keep the current therethrough low. The voltage divider isconnected to a respective one input of the amplifiers A5 and A6 whicheach form one comparator.

The voltage divider is intended to ensure that the system voltage andcondenser voltage are compatible if the normal condenser voltage ishigher than the normal voltage of the system; otherwise, the voltagedivider can be omitted. The lowest voltage at which the electromagnetwill still respond is present at the tapping of R4, R5. If this voltageis higher than the voltage of V_(B1), the small signal is at the outputof A5 and, if it is higher than the voltage of battery V_(B2), the smallsignal is at the output of A6. If the small signal is present at theoutputs of A5 and A6, the small signal is at all inputs of the OR gateG5 and the AND gates G3 and G4 are closed and therefore the switches SW3and SW4 are open. By reason of the negation performed in the NOT elementI₂, the switch SW5 is now closed, so that the storage condensers areconnected to the current supply rail. As soon as the voltage of thecondensers drops below the voltage of one of the batteries V_(B1) andV_(B2), the battery with the higher voltage takes over the supply ofcurrent to the system again in the previously described manner.

If the mechanical switches open momentarily as a result of strongimpacts or oscillations, the condensers C1 and C2 connected to thecurrent supply rail +V or to the feed line V_(T) for the safety circuitsupply the circuits with current for a period which is sufficient forcarrying out all the switching steps. The time necessary for this is nomore than a few microseconds.

We claim:
 1. A power supply system for release circuitry of an electronic ski binding, said system comprising:a first electrical source including a first battery electrically connectable to said release circuitry; a second electrical source including a second battery electrically connectable to said release circuitry; switching means including first switching means connected to said first and second electrical sources, said first switching means being actuable for alternately connecting one of said sources to said release circuitry and the remaining non-connected electrical source(s) being isolated from the connected electrical source, and second switching means for actuating said first switching means in response to selection signals; and comparison means electrically connected to said electrical sources and to said second switching means for continuously monitoring the electrical potentials of said electrical sources and for generating selection signals indicative of the one of said electrical sources having the highest electrical potential, the potentials of said electrical sources defining a floating reference valve as a basis for the generation of said selection signals; said second switching means actuating said first switching means to connect the one of said electrical sources having the highest electrical potential to said release circuitry in response to the generation of said selection signals.
 2. The invention according to claim 1 wherein said system further includes a third electrical source electrically connectable to said circuitry.
 3. The invention according to claim 2 wherein said system further includes means for reducing the load on said third power source in response to the connection of said third electrical source to said release circuitry.
 4. The invention according to claim 2 and further including alarm means for emitting a first alarm signal in response to the connection of said second electrical source to said circuitry, and for emitting a second alarm signal in response to the connection of said third electrical source to said circuitry.
 5. The invention according to claim 2 wherein said third electrical source comprises a capacitor.
 6. The invention according to claim 5 wherein said first switching means comprise mechanical switches for connecting said batteries to said circuitry and an electrical switch for connecting said capacitor to said circuitry and wherein said comparison means includes means for actuating said electrical switch to connect said capacitor to said circuitry in response to the opening of said mechanical switches.
 7. The invention according to claim 1 and further including alarm means for emitting a first alarm signal in response to the connection of said second electrical source to said circuitry.
 8. The invention according to claim 1 and further including:means for initially energizing said power supply system; means for comparing the electrical potential on said first electrical source to a first value; means responsive to the initial energization of said power supply system for maintaining the connection of said first electrical source to said circuitry when the electrical potential of said first electrical source falls below the electrical potential of the other electrical source(s) until the electrical potential of said first electrical source falls to said first value.
 9. A power supply system for release circuitry of an electronic ski binding said system comprising:a first electrical source including a first battery electrically connectable to said release circuitry; a second electrical source including a capacitor electrically connectable to said release circuitry; switching means including first switching means connected to said first and second electrical sources, said first switching means being actuable for alternately connecting one of said sources to said release circuitry and the remaining non-connected electrical source(s) being isolated from the connected electrical source, and second switching means for actuating said first switching means in response to selection signals; and comparison means electrically connected to said electrical sources and to said second switching means for continuously monitoring the electrical potentials of said electrical sources and for generating selection signals indicative of the one of said electrical sources having the highest electrical potential, the potentials of said electrical sources defining a floating reference valve as a basis for the generation of said selection signals; said second switching means actuating said first switching means to connect the one of said electrical sources having the highest electrical potential to said release circuitry in response to the generation of said selection signals.
 10. The invention according to claim 9 wherein said system further includes means for reducing the load on the electrical source connected to said circuitry in response to the connection of said second electrical source to said release circuitry.
 11. The invention according to claim 9 further including alarm means for emitting a first alarm signal in response to the connection of said second electrical source to said circuitry.
 12. The invention according to claim 9 and further including a third electrical source electrically connectable to said circuitry, and alarm means for emitting a first alarm signal in response to the connection of said second electrical source to said circuitry, and for emitting a second alarm signal in response to the connection of said third electrical source to said circuitry.
 13. The invention according to claim 9 wherein said first switching means comprise mechanical switches for connecting said electrical sources to said circuitry and an electrical switch for connecting said capacitor to said circuitry, wherein said comparison means includes means for actuating said electrical switch to connect said capacitor to said circuitry in response to the opening of said mechanical switches.
 14. The invention according to claim 9 and further including:means for initially energizing said power supply system; means for comparing the electrical potential on said first electrical source to a first value; means responsive to the initial energization of said power supply system for maintaining the connection of said first electrical source to said circuitry when the electrical potential of said first electrical source falls below the electrical potential of the other electrical source(s) until the electrical potential of said first electrical source falls to said first value. 